River Landscapes
What Edexcel tells
Detailed
us we need to know.
Content
River processes
Definitions of
produce distinctive
terms should
landforms:
be learnt.
Recognition of
1. Drainage
the features
basin terms:
on diagrams,
watershed,
maps and
confluence,
photographs
tributary, source and but not
mouth.
drainage
basin patterns.
Notes
Student
Check
Drainage Basin: the land drained by a river system.
Watershed: the boundary of a drainage basin, usually made up of
high land.
Confluence: where two rivers meet.
Tributary: smaller rivers which eventually join the main river.
Source: the start of a river, usually in high land.
Mouth: where a river flows into, usually a lake or sea.
Watershed
Confluence
Tributary
Mouth
Source
2. The impact of
weathering,
erosion and mass
movement on river
landscapes.
The processes
should be
understood in
the context of
their role in
forming the
river features
listed in
number 4.
Source
Types of erosion:
 Hydraulic Action: the pressure of the water being pushed
against the bank of a river, forcing cracks apart.
 Corrasion: particles carried by the river are thrown against
the river bank and break down the bank.
 Solution/Corrosion: Acid reaction causes rocks to dissolve.
 Attrition: The wearing away of rocks in a river.
Types of weathering:
*Chemical weathering: Acid in rainwater causes a chemical
reaction in some rocks and they dissolve.
*Physical Weathering: Water gets into cracks in rocks, if it freezes
it expands and the rock cracks.
Biological weathering: Plants grow in the cracks of rocks. As the
plants get bigger the rocks can crack and break.
Mass Movement:
Soil Creep: Gravity will pull water in the soil down a slope,
The soil will move down the slope slowly.
The slope may appear rippled and form terracettes.
Slumping:
Large area of land moving down a slope.
Common on clay river banks; During dry weather the clay cracks
and when it rains, the water runs into cracks and the rock
becomes saturated and heavy, It slips down the slope.
3. Change in
characteristic
s
(width, depth,
velocity,
discharge and
gradient) of
a river and its valley
from
source to mouth.
Understand
the changing
characteristics
in upper,
middle and
lower stages of
the
river valley.
4. The
formation of
interlocking spurs,
waterfalls,
meanders,
river-cliffs, oxbow
lakes,
flood plains and
levees.
Describe the
landforms and
explain
their
formation in
terms of the
sequence
and processes
involved,
including the
influence of
geology.
Rivers can be separated into a upper, middle and lower course.
Channel width: how wide the river channel is. This increases
downstream (increases from the upper to the lower course).
Channel depth: how deep the river channel is. This increases
downstream.
Velocity: the speed of the river. This increases downstream.
Discharge: the amount of water passing a specific point at a given
time (cubic meters). This increases downstream.
Gradient: the slope of the river valley. This decreases
downstream. The river gradient is usually highest in the upper
course by the source.
Upper course:
V-shaped valleys and interlocking spurs:
In the upper course the river is small, and most of the river’s
energy is used to erode downwards, hence the characteristic vshaped valley. As the river winds its way through different rock
types, interlocking spurs form.
Waterfalls:
Waterfall formation:
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The river flows over bands of softer and harder
rocks
Softer rock is more quickly eroded
The river undercuts the harder rock leaving an
overhang
The river forms a plunge pool below the
waterfall.
Water continues to splash up and erode soft
rock through hydraulic action.
Overhanging rock is unsupported and falls into
the plunge pool
The waterfall retreats upstream
This process continues and a gorge is cut back
into the hill.
Middle course:
Meanders:
Water in middle course is directed to outside of the bend. Due to
deeper, faster flowing water erosion takes place on outside of
bend and a river cliff is formed. Deposition occurs on inside of
bend and a slip off slope if formed.
Lower course:
Oxbow lakes
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The river is meandering across the valley
The river is eroding laterally (from side to side)
The river erodes the outside of the bends and deposits on the
inside so its course is changing
This erosion narrows the neck of the meander
Often during a flood the river will cut through the neck
The river continues in the new bed and the meander is
abandoned
New deposition seals off the ends and the cut-off becomes an
ox-bow lake
Floodplains and levees
What are flood plains?
Floodplains are flat valley floors on the banks of rivers
which are layered with silt and alluvium left by the river
flooding
How are floodplains formed?
 A river may overflow its banks during times of
heavy rain.
 When the river recedes, the river deposits the
material it is carrying, leaving behind silt.
 Floodplains are the wide and flat plains formed by
the deposited material or alluvium build up on
either side of the river with successive floods over
the years.
 The heavier and coarser sediments are first
deposited at the river’s edge.
 The finer particles are being deposited a
little further away from the river.
Levees are raised banks of alluvium formed by the
heavier and coarser sediments nearer the river that has
been built by successive floods.
are first deposited at the
Flooding and flood
prevention
5. The physical
and human
causes of river
flooding.
6. The effects of
river
flooding on people
and the
environment.
7. Prediction
and
prevention
of the effects of river
flooding by
forecasting,
building design,
planning
and education.
General
Physical factors:
physical and
- Impermeable rocks mean rainwater cannot soak into the
human factors,
rocks and it therefore flows more quickly into the river.
e.g.
- Steep valley slopes make rainwater run off quickly into the
intensity of
river channel.
rainfall,
- Large amounts of rainfall day after day will saturate the
urbanisation
ground and flow more quickly into the river.
and
Human factors:
deforestation.
- Deforestation leads to less interception of rainfall
therefore it will reach the river more quickly.
- Urbanisation (building settlements or towns) will lead to
more rain reaching the river at a greater speed as many of
the surfaces will be impermeable, will not let the water
soak through.
- Dams may burst flooding large areas.
Effects in
Social Effects: May be temporarily moved away from home, could
relation to
lead to injuries or loss of life.
both the
Environmental Effects: Loss of land, loss of habitats for birds,
human and
amphibians and fish. In Boscastle, trees were washed down the
natural
street.
environments, Economic Effects: high insurance claims, damage to property,
e.g. insurance services, infrastructure. Loss of valuables. In Boscastle, buildings
claims and loss and cars were washed away, some people lost up to 60% of their
of land.
income due to loss of tourism, and a local businessmen lost nearly
£15,000 of stock when his shop flooded.
How the
effects of river
flooding are
reduced
through
planning
before the
event.
-
8. The types of
hard and
soft engineering
Define hard
and soft
engineering.
Websites to give people advice on how to protect homes.
The Met Office and Environment Agent warn people about
the risk of flooding with flood warnings.
- Houses should be not built on flood plains and could be
built on stilts.
Hard Engineering: river flood management that involves major
construction work.
Embankments: raised banks along the river, can be used as a path
used to
control rivers in the
UK
and the advantages
and
disadvantages of
these
techniques.
The main
types of
defence used
on
UK rivers
should be
studied,
including
embankments,
channelisation,
flood
relief
channels,
flood plain
zoning,
washlands,
dams, and
flood warning
systems.
by pedestrians, stops river bank erosion but… they may be ugly
and spoil the view and many embankments are not built high
enough.
Channelisation: river channel widened or deepened to carry more
water, it is long lasting and very effective but… altering the river
may lead to a great risk of flooding downstream and they are
unnatural.
Flood relief channels: the course can be altered diverting the river
away from major settlements, makes people who live close to a
river safer as the water is diverted, and they can be used for water
sports but… they are extremely expensive and require a large
amount of land.
Soft Engineering: river flood management which works or
attempts to work with the natural environment.
Washlands: river is allowed to flood naturally into wasteland areas
to prevent flooding in other areas, they are very cost effective as
nothing is built, and they are a great habitat for birds but… they
require large areas of land that cannot be built on.
Flood warning systems: a network of sirens which give people
early warning of possible flooding through TV’s, radio, email etc. It
is very cheap and effective but… there may not be enough time
for people to prepare and remove valuables.
River management
Examine a case River Nene – Northampton:
9. How a river
study to
- In 2002 4m high floodwalls were installed to protect
is managed in describe and
housing and the railway station.
a named location.
explain the
- In 2003 the warning system was upgraded, aiming to give
management
residents at least two hours notice of a possible flood.
of a riverine
- In 2002 a 450m clay embankment was built in Weedon
area. The
raising the level of the land by 6.8m. This cost £2million.
management
- In 2007 a washland was created in Upton to create an area
should be
where water can be diverted from the River Nene in a
focused on an
controlled manner to reduce the risk of flooding
area of river.
downstream in the town of Northampton.